Power supply circuits can be implemented in a variety of different ways. Examples of power supply circuits include synchronous rectifier power converters, asynchronous rectifier power converters, resonant power converters, and any of a variety of other types of switching power converters. Some power circuits can implement a capacitive charge pump to control the connection of a supply voltage across a load. For example, a variable switching voltage can be provided to the capacitive charge pump device to charge the capacitive charge pump device in a first switching phase, such that the capacitive charge pump device is discharged in a second switching phase to provide the charge to the load.